Pollen morphology and viability in Bromeliaceae

ABSTRACT Pollen morphology characterization is important in taxonomy, conservation and plant breeding, and pollen viability studies can support breeding programs. This study investigated pollen morphology and male fertility in 18 species of Bromeliaceae with ornamental potential. For morphological characterization, pollen grains were acetolyzed and characterization of exine was done using scanning and transmission electron microscopy. Pollen viability was investigated by in vitro germination and histochemical tests. Species belonging to Aechmea and Ananas genera presented medium size pollen, except for Ae. fasciata, with large pollen. Al. nahoumii, P. sagenarius and the Vriesea species analyzed showed large pollen, except for V. carinata, with very large pollen. Pollen of Aechmea, Ananas and P. sagenarius presented bilateral symmetry, diporate, exine varying from tectate to semitectate. Al. nahoumii and Vriesea species presented pollen with bilateral symmetry, monocolpate; exine was semitectate, reticulate and heterobrochate. Germination percentage and tube growth were greater in SM and BKM media. Histochemical tests showed pollen viability above 70% for all species, except for Ananas sp. (40%). Pollen morphology is important for the identification of species, especially in this family, which contains a large number of species. High rates of viability favor fertilization and seed production, essential for efficient hybrid production and conservation.

Description of the immatures of Linepithema humile Mayr (Hymenoptera: Formicidae)

Linepithema humile Mayr is an ant species originally native to South America that has been spread accidently throughout the globe through international trade. It is a serious urban and crop pest. Despite its economic importance, little is known about the larvae of this species apart from a brief description based on a few specimens. The present investigation is aimed at describing every immature stage of L. humile. Three larval instars were determined through the frequency distribution of the maximum width of head capsules from a sample of 525 larvae. The morphological descriptions were based on 150 eggs, 70 larvae, and 90 pupae examined by light and scanning electron microscopy. Some morphological characteristics reported to be typical of Linepithema Mayr larvae were confirmed - dolichoderoid body shape, presence of dorsal protuberance, sparse simple body hairs, presence of nine pairs of spiracles and dolichoderoid mandibles. We concluded that an earlier published description was based on queen larvae, and that the protuberance is only present in worker larvae. The information provided in this study may aid ant systematics and phylogenetics, as well provide a better understanding of the biology of this species.

Efeito da aplicação de silício em plantas de milho no desenvolvimento biológico da lagarta-do-cartucho Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) / Effect of silicon application on corn plants upon the biological development of the fall armyworm Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae)

The effect of the application of silicon to corn plants on the development of the fall armyworm Spodoptera frugiperda (J.E. Smith) was evaluated. Silicon treatment consisted in applying 3.2 ml of a sodium silicate solution [25-28 percent (w/v) SiO2] plus 96.8 ml of water into the soil at 5, 10, 15, 20 and 25 days after emergence of corn plants kept in pots. Another group of plants were grown free of silicon. Larvae were fed on leaves obtained from silicon treated plants and their mortality at the end of the 2nd larval instar, length of the larval and pupal period, and pupal weight were compared to those of larvae fed on normal leaves. No effect of silicon was observed on the length of larval and pupal phase, pupal weight and mortality of pupae. However, increased mortality and cannibalism were registered in groups of fall armyworm at the end of the 2nd instar and greater mortality of the larvae was seen at the 2nd and 6th instars fed on silicon-treated corn plant leaves in comparison with the control. The jaws mandibles of fall armyworm at the 6th instar showed marked wear on the incisor region when in contact with leaves with higher silicon content. Silicon application can make fall armyworm feeding difficult, causing higher mortality and cannibalism, thus increasing plant resistance to this species.

Este trabalho, objetivou avaliar o efeito da aplicação de silício em plantas de milho no desenvolvimento da lagarta-do-cartucho Spodoptera frugiperda (J.E. Smith). O tratamento com silício consistiu na aplicação de 3,2 ml de solução de silicato de sódio [25-28 por cento (p/v) de SiO2], mais 96,8 ml de água, via solo aos cinco dias, 10, 15, 20 e 25 dias após a emergência de plantas de milho mantidas em vasos. Outro grupo de plantas foi cultivado sem aplicação de silício. Avaliou-se o desenvolvimento de lagartas alimentadas com folhas de milho retiradas de plantas tratadas com silício, em comparação com lagartas alimentadas com folhas de milho não tratadas, registrando-se a mortalidade ao final do 2° ínstar larval, a duração do período larval e pupal, a mortalidade larval e pupal e o peso de pupa. Não se observou efeito do silício na duração da fase larval e pupal, peso de pupa e na mortalidade de pupas. Entretanto, verificou-se maior mortalidade e aumento de canibalismo em grupos de lagartas ao final do 2° ínstar, e maior mortalidade de lagartas individualizadas no 2° e 6° ínstares, quando foram alimentadas com folhas de plantas de milho tratadas com silício, em comparação com a testemunha. Observou-se que as mandíbulas das lagartas, nos seis ínstares, apresentaram desgaste acentuado na região incisora quando em contato com folhas com maior teor de silício. A aplicação de silício pode dificultar a alimentação de lagartas, causando aumento de mortalidade e canibalismo e, portanto, tornando as plantas de milho mais resistentes à lagarta-do-cartucho.